NO-cGMP pathway in penile corpus cavernosal smooth muscle plays an importan
t role in penile erection. The level of cGMP is regulated by a balance betw
een the rate of synthesis by guanylate cyclase and the rate of hydrolytic b
reakdown to guanosine 5' monophosphate (GMP) by phosphodiesterase 5(PDE5).
Icariin is isolated from natural drug Epimedii herba, it is shown to have t
he relaxation effect on corpus cavernosal smooth muscle of rabbit (IC50: 4x
10(-4) mol/L), and the mechanism of the relaxation effect of Icariin on cor
pus cavernosum, believed to have the inhibiting effect on PDE5 and activati
on of NO-cGMP pathway to enhancing penile erection.